The following discussion of the background to the invention is intended to facilitate an understanding of the present invention. However, it should be appreciated that the discussion is not an acknowledgment or admission that any of the material referred to was published, known or part of the common general knowledge in any jurisdiction as at the priority date of the application.
The heart's electrical system controls the rate and rhythm of the heartbeat. With each heartbeat, an electrical signal spreads from the atria of the heart to the ventricles of the same. As the electrical signal travels via the atria, it causes the heart to contract and pump blood into the ventricles. The frequency of electrical signals then reduces to allow the ventricles time to finish filling with blood before signalling the ventricles to contract and pump blood to the lungs and the rest of the body. The ventricles then relax and the heartbeat process restarts all over again.
In a normal heart, the electrical signal is fired off 60 to 100 times a minute—this is the heart rate or pulse. A problem with any part of the heartbeat process can cause an arrhythmia or an irregular heartbeat. The heart may beat too fast, too slowly, too early or too irregularly. For example, in a type of Arrhythmia known as atrial fibrillation, the electrical signals travel through the atria in a fast and disorganized way, causing the atria to quiver instead of contract, leading to an irregularly irregular heartbeat.
Atrial fibrillation (AF) is classified under a category of illness known as cardiac arrhythmia, which is an electrical signal disturbance in the heart causing it to beat erratically. Normally, the heart beats in a steady rhythm often referred to as a sinus rhythm. However, AF interferes the normal regular electrical impulses generated by the sinoatrial node and are overwhelmed by disorganized electrical impulses. This causes the heart to beat inefficiently and contractions of the heart are weaker than normal contractions, resulting in slow flow of blood. AF may occur in episodes lasting from minutes to days (“paroxysmal”), or be permanent in nature.
Due to the irregularity of heartbeat caused by AF, the blood in the heart pools and becomes sluggish or increased turbulence that can result in the blood clotting (thrombus) in the grooves of the heart. Most commonly, atrial fibrillation causes strokes where in the event that a clot leaves the heart and travels to the brain (emboli), blocking the flow of blood through cerebral arteries. A stroke occurs when the blood supply to the brain is blocked and this starves the brain of oxygen and nutrients. This cuts off the blood flow to an area of the brain, damaging the brain cells by starving them of oxygen. This can lead to brain damage occurring and, depending how long the blood supply is cut off, this may be temporary or permanent. Emboli in the brain may result in an ischemic stroke or a transient ischemic attack.
Ischemic Strokes are caused by an interruption of blood flow to the brain because of a blood clot. There are two kinds of ischemic stroke:                Thrombotic—caused by a blood clot in an artery leading directly to the brain        Embolic—caused by a blood clot that travels to the brain from somewhere else in the body.        
The conventional method of detecting such conditions has been to use an electrocardiogram (ECG) connected to the patient's chest via electrodes. The ECG records the electrical activity and rhythms of the patient's heart and impulses are recorded as waves and displayed on a screen (or printed on paper). Such ECG devices can be large, cumbersome and non-portable, rendering the patient immobile for the period of measurement, which can be especially difficult in detecting arrhythmia (which occurs irregularly) for prolonged periods of time, in particular if arrhythmia is to be detected over 24 hours or more, or whether arrhythmia is triggered or aggravated by performing certain activities. In addition, ECG may be subjected to errors arising from mechanical-electrical dissociation—i.e. continued electrical rhythmicity of the heart in the absence of effective mechanical function.
A separate problem exists with respect to the methods used for detection of arrhythmia. Present methods are generally device-specific and require complex mathematical manipulations on the signal obtained. There thus exists a need to improve on such methods to reduce the complexity and compatibility with other devices.
It is thus an object of the invention to at least alleviate the above mentioned problems.